Getting "unknown host name ..." complied with static library ?

i'm using MingW (windows) to compile libpq program.
if i used dynamic library (-lpqdll), the program can be
compiled and running well (i can access the database).
but, if i used static library (-lpq), 
the program can be compiled, but can't access the database.
the error message is "unknown host name: 192.168.1.1".

What's wrong and how to handle it ?

thanks